Organic electroluminescent element material, organic electroluminescent element, method of manufacturing organic electroluminescent element, display device, and illuminating device

ABSTRACT

In the present invention, provided is an organic electroluminescent element material having a high externally taking-out quantum efficiency, which is suitable for manufacturing an element exhibiting long light emission lifetime, and also provided is an organic electroluminescent element possessing the material, a method of manufacturing the organic electroluminescent element, and a display as well as an illuminating device fitted with the organic electroluminescent element.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent elementmaterial, an organic electroluminescent element, a method ofmanufacturing an organic electroluminescent element, a display deviceand an illuminating device.

BACKGROUND

As an emission type electronic displaying device, there is anelectroluminescent display (hereinafter referred to as ELD). As devicesconstituting the ELD, there are mentioned an inorganicelectroluminescent element and an organic electroluminescent element(hereinafter referred to as organic EL element).

The inorganic electroluminescent element has been used for aplane-shaped light source, but a high voltage alternating current hasbeen required to drive the element.

An organic EL element has a structure in which a light emission layercontaining a light emission compound is arranged between a cathode andan anode, and an electron and a hole are injected into the lightemission layer and recombined to form an exciton. The element emitslight, utilizing light (fluorescent light or phosphorescent light)generated by inactivation of the exciton, and the element can emit lightby applying a relatively low voltage of from several volts to severaldecade volts. The element has a wide viewing angle and highvisualization since the element is of self light emission type. Further,the element is a thin, complete solid device, and therefore, the elementis noted from the viewpoint of space saving and portability.

However, development of an organic EL element for practical use isdemanded which efficiently emits light with high luminance at a lowerpower.

High emission luminance and long lifetime is attained in Japanese PatentNo. 3093796 by doping a slight amount of a phosphor in stilbenederivatives, distyrylarylene derivatives or tristyrylarylenederivatives.

An element is known which comprises an organic light emission layercontaining an 8-hydroxyquinoline aluminum complex as a host compounddoped with a slight amount of a phosphor in Japanese Patent O.P.I.Publication No. 63-264692, and an element is known which comprises anorganic light emission layer containing an 8-hydroxyquinoline aluminumcomplex as a host compound doped with a quinacridone type dye inJapanese Patent O.P.I. Publication No. 3-255190.

When light emitted through excited singlet state is used as in theabove, the upper limit of externally taking-out quantum efficiency (η)is considered to be at most 5%, as the generation ratio of singletexcited species to triplet excited species is 1:3, that is, thegeneration probability of excited species capable of emitting light is25%, and further, external light emission efficiency is 20%.

Since an organic EL element, employing phosphorescence through theexcitation triplet, was reported by Prinston University (see M. A. Baldoet al., Nature, 395, p. 151-154 (1998)), study on materials emittingphosphorescence at room temperature has been actively made.

For example, such an organic EL element is disclosed in M. A. Baldo etal., Nature, 403, 17, p. 750-753 (2000) or U.S. Pat. No. 6,097,147.

As the upper limit of the internal quantum efficiency of the excitationtriplet is 100%, the light emission efficiency of the excitation tripletis theoretically four times that of the excited singlet. Such an organicEL element has possibility that exhibits the same performance as a coldcathode tube, and its application to illumination is watched.

Many compounds, mainly heavy metal complexes such as iridium complexesare synthesized and studied in for example, S. Lamansky et al., S. Am.Chem. Soc., 123, 4304 (2001).

An example employing tris(2-phenylpyridine)indium as a dopant is studiedin M. A. Baldo et al., Nature, 403, 17, p. 750-753 (2000) above.

Further, M. E. Tompson et. al. studies an example employing as a dopantL₂Ir (acac) such as (ppy)₂Ir (acac) in The 10^(th) InternationalWorkshop on Inorganic and Organic Electroluminescence (EL' 00,Hamamatsu), and Moon-Jae Youn. Og, Tetsuo Tsutsui et. al. an exampleemploying as a dopant tris(2-p-tolylpridine)iridium {Ir(ptpy)₃} ortris(benzo-[h]-quinoline)iridium {Ir(bzq)₃} in The 10^(th) InternationalWorkshop on Inorganic and Organic Electroluminescence (EL' 00,Hamamatsu). In addition, these metal complexes are generally calledorthometalated iridium complexes.

As described above, attempt for preparing an element employing variousiridium complexes is made in S. Lamansky et al., J. Am. Chem. Soc., 123,4304 (2001) or in Japanese Patent O.P.I. Publication No. 2001-247859.

Further, to obtain high emission efficiency, Ikai et al. utilized a holetransporting compound as a host of a phosphorescent compound at The 10thInternational Workshops on Inorganic and Organic Electroluminescence(EL'00, Hamamatsu). Further, M. E. Tompson et al. utilized various typesof electron transporting materials doped with a new iridium complex as ahost of a phosphorescent compound.

An organic EL element fitted with the iridium complex is preparedgenerally via evaporation. Studies of an organic EL element prepared bya coating method have been actively done, but it is presently difficultto prepare the organic EL element via coating since the iridium complexexhibits low solubility. Thus, it is desired to improve solubility ofthe iridium complex.

Further, orthometalated complexes in which iridium as a center metal isreplaced by platinum are also watched. Regarding these complexes, thereare known many kinds of complexes having characteristics in the ligands,which are disclosed in Japanese Patent O.P.I. Publication Nos.2002-332291, 2002-332292, 2002-338588, 2002-226495, and 2002-234894, forexample.

Light emission elements employing the above compounds exhibit greatlyimproved emission luminance and emission efficiency as compared toconventional elements, because the light emission arises fromphosphorescence, but they have a problem in that emission lifetime islow as compared to conventional elements. In this way, in the case of alight emitting material exhibiting high phosphorescence efficiency, itis difficult to improve realization of shorter light emission wavelengthas well as emission lifetime, whereby presently, practically sufficienttolerable performance has not yet been achieved.

As a material to improve the performance, for example, known is an Ircomplex or a Pt complex each having a phenyl imidazole derivative as aligand in WO 02/15645 and WO 05/7767. However, light emission efficiencyand lifetime of the element of each of these complexes are notsufficiently satisfactory, and further improvement of the light emissionefficiency and the lifetime are desired to be improved.

A vacuum evaporation method is conventionally utilized as a method ofmanufacturing an organic EL element, but since in the case of theconventional vacuum evaporation method, high vacuum is required for theoperation, the manufacturable member is limited in size, and a step oftaking a member in and out is also required at the same time. Thus, theconventional vacuum evaporation method is rejected as unsuitable for thecontinuous production.

On the other hand, as a continuously manufacturable means, a method ofemploying an EL material solution is disclosed (refer to Patent Document1, for example), and a low-molecular material and a polymeric materialare to be usable as the EL material.

However, in the case of coating with a low-molecular material, a lowerlayer and an upper layer are difficult to be incorporated duringformation of a multilayer, resulting in difficulty of obtaining an ELelement exhibiting high performance.

Further, in the case of a polymeric material, there appears a problemsuch that a refining method available with a low-molecular material suchas a recrystallization method, a sublimation refining method, and asilica column refining method can not be utilized, and impuritiescontained in a monomer as raw material to prepare a polymer aredifficult to be removed. Thus, this reason leads to a factor to degradelight emission lifetime.

Patent Document 1: Japanese Patent O.P.I. Publication No. 2001-297882

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

It is an object of the present invention to provide an organicelectroluminescent element material having a high externally taking-outquantum efficiency, which is suitable for manufacturing an elementexhibiting long light emission lifetime, and also to provide an organicelectroluminescent element possessing the material, a method ofmanufacturing the organic electroluminescent element, and a display aswell as an illuminating device fitted with the organicelectroluminescent element.

Means to Solve the Problems

The above-described object of the present invention is accomplished bythe following Structures.

(Structure 1) An organic electroluminescent element material comprisinga synthesized polymer from at least one monomer having an impuritycontent of 1000 ppm or less.

(Structure 2) The organic electroluminescent element material ofStructure 1, wherein the at least one monomer has an impurity content of100 ppm or less.

(Structure 3) The organic electroluminescent element material ofStructure 1 or 2, wherein the at least one monomer comprises a reactivesubstituent.

(Structure 4) The organic electroluminescent element material of any oneof Structures 1-3, the polymer comprises a partial structure representedby the following Formula (1):

—Ar1-N(Ar3)-Ar2-  Formula (1)

wherein each of Ar1 and Ar2 independently represents an arylene group ora heteroarylene group, and Ar3 represents an aromatic hydrocarbon groupor an aromatic heterocyclic group.

(Structure 5) An organic electroluminescent element comprising theorganic electroluminescent element material of any one of Structures1-4.

(Structure 6) The organic electroluminescent element of Structure 5,comprising a phosphorescence emission compound.

(Structure 7) The organic electroluminescent element of Structure 5 or6, prepared with a solution comprising the organic electroluminescentelement material of any one of Structures 1-4.

(Structure 8) The organic electroluminescent element of any one ofStructures 5-7, producing white light emission.

(Structure 9) A method of manufacturing an organic electroluminescentelement, comprising the step of using a reaction solution for a polymerto be synthesized from at least one monomer having an impurity contentof 1000 ppm or less to prepare the organic electroluminescent element ofany one of Structures 5-8.

(Structure 10) A display device comprising the organicelectroluminescent element of any one of Structures 5-8.

(Structure 11) An illuminating device comprising the organicelectroluminescent element of any one of Structures 5-8.

EFFECT OF THE INVENTION

In the present invention, provided can be an organic electroluminescentelement material having a high externally taking-out quantum efficiency,which is suitable for manufacturing an element exhibiting long lightemission lifetime, and also provided can be an organicelectroluminescent element possessing the material, a method ofmanufacturing the organic electroluminescent element, and a display aswell as an illuminating device fitted with the organicelectroluminescent element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of a display devicecomposed of an organic EL element.

FIG. 2 is a schematic diagram showing display section A.

FIG. 3 is a schematic diagram showing a pixel.

FIG. 4 is a schematic diagram showing a passive matrix system full colordisplay device.

FIG. 5 is an appearance diagram showing an illuminating device.

FIG. 6 is a schematic diagram showing an illuminating device.

EXPLANATION OF NUMERALS

-   1 Display-   3 Pixel-   5 Scanning line-   6 Data line-   7 Power supply line-   10 Organic EL element-   11 Switching transistor-   12 Drive transistor-   13 Condenser-   A Display section-   B Control section-   101 Organic EL element-   102 Glass cover-   105 Cathode-   106 Organic EL layer-   107 Glass substrate provided with transparent electrode-   108 Nitrogen gas-   109 Water refilling agent

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As to an organic electroluminescent element material of Structure 1 or 2in the present invention, provided is a polymer synthesized from atleast one monomer having an impurity content of 1000 ppm or less, or anorganic electroluminescent element material containing a synthesizedpolymer from at least one monomer having an impurity content of 1000 ppmor less, and also provided can be an organic electroluminescent elementexhibiting high externally taking-out quantum efficiency and long lightemission lifetime via use of the foregoing element material, and adisplay device and an illuminating device fitted with the foregoingelement.

Next, each of constituent elements in the present invention will bedescribed is detailed in order.

<<Monomer Having Impurity Content of 1000 ppm or Less>>

A monomer having comprised in an organic electroluminescent elementmaterial of the present invention will be described.

The monomer of the present invention is referred to also as an organiccompound having a reactive substituent, and has an impurity content of1000 ppm or less, but preferably has an impurity content of 100 ppm orless.

Herein, to achieve the impurity content of 1000 ppm or less means that amonomer of the present invention (an organic compound having a reactivesubstituent) is designed to have a purity content of 99.9% by weight ormore.

In the present invention, it is inhibited by using an organicelectroluminescent element material containing a high-purity polymersynthesized from the above-described high-purity monomer (organiccompound having a reactive substituent) to contain the impurity topossibly induce poor performance variation of an organicelectroluminescent element, whereby light emission efficiency andlifetime of the element become possible to be largely improved.

{Measurement of Impurity Content (Referred to Also as Measurement ofPolymer Purity)}

The purity of a monomer of the present invention (an organic compoundhaving a reactive substituent) can be measured and determined by acommercially available HPLC (high performance liquid chromatography).

The monomer purity measured by HPLC will be described in detail insynthetic examples of the after-mentioned monomer.

(Reactive Substituent)

The reactive substituent of the present invention will be described.

Specific examples of the reactive substituent of the present inventioninclude groups each having the following partial structure.

As organic compounds each having the above-described reactivesubstituent, preferable compounds are those having the above-describedreactive group as mother compounds such as compounds used for forming ahost compound, an emission dopant, a fluorescence dopant, an electioninjection layer and a hole injection layer; compounds used for fanning ahole blocking layer and an electron blocking layer; compounds used forforming a hole transport layer; and compounds used for forming anelectron transport layer, which are utilized to form a constituent layerof the after-mentioned organic electroluminescent element (organic ELelement).

Further, these can also be appropriately selected from compoundsdescribed as a hole transport material, an electron blocking material,an emission host (referred to as a host compound), an emission dopant(referred to simply as a dopant), an electron transport material and ahole blocking material, and compounds disclosed in patent documents.

Specific examples of the compound having a reactive substituent areshown below, but the present invention is not limited thereto.

Next, a synthetic example of the monomer relating to an organicelectroluminescent element material of the present invention (an organiccompound having a reactive substituent) will be shown, but the presentinvention is not limited thereto.

Synthetic Example Synthesis of Compound 1-2

Into a 200 mL three-necked flask, added were 0.5 g of palladium acetate,100 mL of xylene, and 1.0 g of tri-tert-butylphosphine, and the systemwas replaced by introducing nitrogen, followed by stirring at roomtemperature for 30 minutes. Thereafter, 5.2 g of 4,4′-diiodobiphenyl,5.0 g of 3-formylcarbazole (compound described in J. Chem. Soc., 1957,2210-2212), and 3.0 g of tert-buthoxy sodium were added therein, andheated to reflux for 5 hours.

After completing the reaction, the system was cooled to roomtemperature, and an insoluble substance was removed via diatomitefiltration. It was washed with saturated saline and dried with sodiumsulfate, and was subsequently concentrated at reduced pressure with arotary evaporator.

A residue was purified by silica gel chromatography to obtain 5.5 g ofcompound 1-2 as a formyl substance {referred to also as compound 1-2(formyl)}.

Next, 4.0 g of methyltriphenylphosphonium bromide and 80 mL oftetrahydrofuran were added in a 200 mL three-necked flask, and theinside of the system was cooled to −70° C. or less after replacing thereaction system with nitrogen. Then, after 6.0 mL of a 2 mol/L LDA wereadded into the system, it was once raised up to a temperature of 0° C.

After cooling this reaction system to −70° C. or less again, 20 mL of aTHF solution obtained from 5.5 g of compound 12 as a formyl substance{referred to also as compound 1-2 (formyl)} were dropped at −70° C. orless while stirring for one hour.

After completion of stirring, the system was heated back to roomtemperature. The reaction solution was washed with saturation saline,dried with magnesium sulfate, and subsequently concentrated at reducedpressure with a rotary evaporator.

The residue was purified by silica gel chromatography to obtain 2.2 g ofa white solid, and it was confirmed via determination of themass-spectrum and ¹H-NMR spectrum that the resulting was compound 1-2.

(Preparation of Compound 12 Having Different Purity Content)

The purity of this target material was measured via HPLC, resulting in apurity content of 96.30% (compound 1-2a). This white solid was purifiedagain via silica gel chromatography, resulting in a purity content of98.02% (compound 1-2b) obtained via HPLC.

Recrystallization was subsequently repeated 3 times (1^(st) time: apurity content of 99.53% obtained via HPLC (compound 1-2c), 2^(nd) time:a purity content of 99.92% obtained via HPLC (compound 1-2d), and 3^(rd)time: a purity content of 99.99% obtained via HPLC (compound 1-2d).Compounds 1-2 each having a different purity content were obtained.

Next, the measurement conditions of HPLC employed in the presentinvention are shown below.

Measurement Conditions of HPLC

Measuring apparatus: LC-2000 Series (manufactured by Japan AnalyticalIndustry Co., Ltd.)Utilized column: ODS-3 (GL Science)Developing solvent: acetonitrile/water=3/7Developing flow: 1 mL/min

Temperature: 40° C.

Detection wavelength: 254 nm

A monomer having an impurity content of 1000 ppm in the presentinvention (referred to also as an organic compound having a reactivesubstituent) can be synthesized by using, for example, a methoddisclosed in Japanese Patent O.P.I. Publication No. 2004-327454 or thereference described in the foregoing documents.

<<Polymer Having Partial Structure Represented by Formula (1)>>

Further, a polymer of the present invention, synthesized by using atleast one monomer having an impurity content of 1000 ppm or less,preferably has a partial structure represented by foregoing Formula (1).

Examples of an arylene group independently represented at each of Ar1and Ar2 in Formula (1) include an o-phenylene group, a m-phenylenegroup, a p-phenylene group, a naphthalenediyl group, an anthracenediylgroup, a naphthacenediyl group, a pyrenediyl group, anaphthylnaphthalenediyl group, a biphenyldiyl group (for example, a[1,1′-biphenyl]-4,4′-diyl group and a 3,3′-biphenyldiyl group, and a3,6-biphenyldiyl group), terphenyldiyl group, quaterphenyldiyl group, aquinquephenyldiyl group, a sexiphenyldiyl group, a septiphenyldiylgroup, an octiphenyldiyl group, a nobiphenyldiyl group, and adeciphenyldiyl group. Further, The foregoing arylene group may also havea substituent.

As the heteroarylene group independently represented at each of Ar1 andAr2 in Formula (1), provided is a divalent group derived from the groupconsisting of a carbazole group, a carboline ring, a diazacarbazole ring(also referred to as a monoazacarboline group, indicating a ringstructure formed in such a manner that one of the carbon atomsconstituting the carboline ring is replaced with a nitrogen atom), atriazole ring, a pyrrole ring, a pyridine ring, a pyrazine ring, aquinoxaline ring, a thiophene ring, an oxadiazole ring, a dibenzofuranring, a dibenzothiophene ring and an indole ring.

Further, The foregoing heteroarylene group may also have a substituent.

Examples of the aromatic hydrocarbon ring group (referred to also asaromatic hydrocarbon group or aryl group) represented at Ar3 in Formula(1) include a phenyl group, a p-chlorophenyl group, a mesityl group, atolyl group, a xylyl group, a naphthyl group, an anthryl group, anazulenyl group, an acenaphthenyl group, a fluorenyl group, a phenanthrylgroup, an indenyl group, a pyrenyl group, and a biphenyl group. Thesegroups each may be unsubstituted, or may have a substituent.

Examples of the aromatic heterocyclic group represented at Ar3 inFormula (1) include a pyridyl group, a pyrimidinyl group, a furyl group,a pyrrolyl group, an imidazolyl group, a benzimidazolyl group, apyrazolyl group, a pyrazinyl group, a triazolyl group (for example, a1,2,4-triazole-1-yl group or a 1,2,3-triazole-1-yl group), an oxazolylgroup, a benzoxazolyl group, a thiazolyl group, an isooxazolyl group, anisothiazolyl group, a furazanyl group, a thienyl group, a quinolylgroup, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, adibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinylgroup, a diazacarbazolyl group (in which one of the carbon atomsconstituting the carboline ring of the carbolinyl group is substitutedwith a nitrogen atom), a quinoxalinyl group, a pyridazinyl group, atriazinyl group, a quinazolinyl group, and a phthalazinyl group.

These groups each may be unsubstituted, or may have a substituent.

Next, specific examples of the polymer having a partial structurerepresented by Formula (1) in the present invention will be shown, butthe present invention is not limited thereto.

<<Method of Manufacturing Organic EL Element>>

The method of manufacturing an organic EL element of the presentinvention will be described.

As an example of the method of manufacturing an organic EL element ofthe present invention, a method of manufacturing an organic EL elementcomposed of anode/hole injection layer/hole transport layer/lightemission layer/hole blocking layer/electron transport layer/cathodebuffer layer/cathode will be described. A specific method ofmanufacturing an organic EL element will be described in Example indetail.

A monomer (organic compound having a reactive substituent) having animpurity content of 1000 ppm or less, concerning an organicelectroluminescent element material (organic EL element material) of thepresent invention, is usable to form any one of a hole injection layer,a hole transport layer, a light emission layer, a hole blocking layer,an electron transport layer and a cathode buffer layer described above,if desired.

First, a thin film made of a desired electrode material such as an anodematerial, for example, is formed on a substrate via evaporation orsputtering so as to give a film thickness of not more than 1 μm, butpreferably 10-200 nm to prepare an anode. Next, a thin layer containingan organic compound as an element material constituting a hole injectionlayer, a hole transport layer, a light emission layer, a hole blockinglayer or an electron transport layer is formed thereon.

Examples of the method of forming a thin film containing the organiccompound (referred to also as an organic compound layer or an organiclayer) include a spin coating method, a cast method, an inkjet method, avacuum evaporation method and a printing method, but a vacuumevaporation method or a spin coating method is specifically preferablein view of easy preparation of a homogeneous layer and reducedgeneration of pinholes.

Further, a different film formation method may be separately applied toeach layer. When the evaporation method is applied for film formation,the evaporation conditions depend on kinds of utilized compounds, but ingeneral, preferably selected are a boat heating temperature of 50-450°C., a vacuum degree of 10⁻⁶-10⁻² Pa, a deposition rate of 0.01-50nm/sec, a substrate temperature of −50-300° C. and a film thickness of0.1-5 μm.

After forming these layers, a 1 μm or less thick thin film made of acathode material is formed thereon via evaporation or sputtering so asto preferably give a film thickness of 50-200 mm to obtain a desiredorganic EL element via formation of a cathode.

This organic EL element is preferably prepared in one time of evacuationfor all steps of from a hole injection layer to a cathode, but adifferent film formation method may also be allowed to be used afterremoving the sample in the preparation on the way. In this case, theoperation is preferably conducted in dry inert gas atmosphere.

<<Constituent Layer of organic EL Element>>

As an element prepared by a method of manufacturing an organic thin filmelement of the present invention, provided is an organicelectroluminescent element (organic EL element) as an example.

The constituent layer of an organic EL element of the present invention(referred to also as an organic layer or an organic compound layer), andan inorganic layer (referred to also as an inorganic compound layer)will be described. In the present invention, preferred examples of layerconfiguration of the organic EL element of the present invention will bespecifically shown below, but the present invention is not limitedthereto.

(i) anode/light emission layer/electron transport layer/cathode(ii) anode/hole transport layer/light emission layer/electron transportlayer/cathode(iii) anode/hole transport layer/light emission layer/hole blockinglayer/electron transport layer/cathode(iv) anode/hole transport layer/light emission layer/hole blockinglayer/electron transport layer/cathode buffer layer/cathode(v) anode/anode buffer layer/hole transport layer/light emissionlayer/hole blocking layer/electron transport layer/cathode bufferlayer/cathode

In the organic EL element of the present invention, a blue emissionlayer preferably has an emission maximum wavelength of 430-480 nm, agreen emission layer preferably has an emission maximum wavelength of510-550 nm, and a red emission layer preferably has an emission maximumwavelength of 600-640 nm, and a display employing these layers ispreferred. At least these three layers may be laminated in order toprepare a white emission layer. A non-light emission layer may beprovided as an intermediate layer between these emission layers. It ispreferred that the organic EL element of the invention is a whiteemission layer or an illuminating device employing the same.

Each layer constituting the organic EL element of the present inventionwill be described.

<<Light Emission Layer>>

The light emission layer in the present invention is a layer whereelectrons and holes, injected from electrodes, an electron transportlayer or a hole transport layer, are recombined to emit light. Theportions where light emits may be in the light emission layer or at theinterface between the light emission layer and the layer adjacentthereto.

The total thickness of the light emission layer is not specificallylimited. In view of improving layer uniformity and stability of emissioncolor against driving electric current without requiring unnecessaryhigh voltage on light emission, the above thickness is adjusted to be inthe range of preferably from 2 nm to 5 μm, more preferably from 2 nm to200 nm, and still more preferably from 10 nm to 20 nm.

Employing an emission dopant or a host compound each described later,the light emission layer is formed according to a known thin layerformation method such as a vacuum evaporation method, a spin coatingmethod, a cast method, an LB method or an inkjet method.

The light emission layer of the organic EL element of the presentinvention preferably contains a host compound and at least one kind ofan emission dopant (referred to also as phosphorescence dopant or aphosphorescence emission dopant) and a fluorescence dopant.

{Host Compound (Referred to Also as Emission Host)}

The host compound used in the present invention will be described below.

Herein, the host compound in the present invention is defined as acompound which is contained in the light emission layer in an amount of20% by weight or more and which has a phosphorescence quantum yield atroom temperature (25° C.) of less than 0.1. The phosphorescence quantumyield of the host compound is preferably less than 0.01. The content ofthe host compound in the light emission layer is preferably 20% byweight or more.

As a host compound, a commonly known host compound may be used singly,or in combination with plural kinds. It is possible to control thetransfer of charges by making use of a plurality of host compounds,resulting in high efficiency of an organic EL element. In addition, itis possible to mix different emission lights by making use of aplurality of the after-mentioned emission dopants. Any emission colorcan be appropriately obtained thereby.

The structure of the emission host in the present invention is notspecifically limited, but typical examples thereof include carbazolederivatives, triarylamine derivatives, aromatic borane derivatives,nitrogen-containing heterocyclic compounds, thiophene derivatives, furanderivatives, those having a moiety such as an oligoarylene compound,carbolise derivatives, and derivatives each having a ring structure inwhich at least one of the carbon atoms of the hydrocarbon ringconstituting a carboline ring of the foregoing carboline derivatives isreplaced by a nitrogen atom.

Of these, preferable usable are carbazole derivatives, carbolinederivatives, and derivatives each having a ring structure in which atleast one of the carbon atoms of the hydrocarbon ring constituting acarboline ring of the foregoing carboline derivatives is replaced by anitrogen atom.

Specific examples are shown below, but the present invention is notlimited thereto. It is preferable that these compounds are also used asthe hole blocking material.

A commonly known host compound which may be used in combination ispreferably a compound having hole transporting ability and electrontransporting ability, as well as preventing longer light emissionwavelength and having a high Tg (a glass transition temperature).

As specific examples of the commonly known host compound, compoundsdescribed in the following documents are cited.

For example, Japanese Patent O.P.I. Publication Nos. 2001-257076,2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786,2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056,2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568,2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453,2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861,2002-280183, 2002-299060, 2002-302516, 2002-305083, 2002-305084, and2002-308837.

(Emission Dopant)

The emission dopant in the present invention will be described.

As the emission dopant in the present invention, a compound having apartial structure represented by the foregoing Formula (1) or a compoundhaving a partial structure represented by the foregoing Formula (2) ispreferably usable as a phosphorescence dopant.

Further, as the emission dopant in the present invention, commonly knownfluorescence dopant (also referred to as a fluorescent compound) andphosphorescence dopant (also referred to as a phosphorescence emitter, aphosphorescent compound or a phosphorescence emission compound) areusable.

(Phosphorescence Dopant)

The phosphorescence dopant in the present invention will be described.

The phosphorescence dopant in the present invention is a compound whichemits light from the excitation triplet, can emit phosphorescence atroom temperature (25° C.), and has a phosphorescent quantum yield at 25°C. of 0.01 or more. The phosphorescent quantum yield at 25° C. ispreferably 0.1 or more.

The phosphorescent quantum yield can be measured according to a methoddescribed in the fourth edition “Jikken Kagaku Koza 7”, Bunko II, page398 (1992) published by Maruzen. The phosphorescent quantum yield can bemeasured in a solution employing various kinds of solvents. Thephosphorescence dopant in the present invention is a compound, in whichthe phosphorescent quantum yield measured employing any one of thesolvents satisfies the above-described definition (at least 0.01).

The light emission of the phosphorescence dopant is divided into twotypes in principle, one is an energy transfer type in whichrecombination of a carrier occurs on the host to which the carrier istransported to excite the host, the resulting energy is transferred tothe phosphorescence dopant, and light is emitted from thephosphorescence dopant, and the other is a carrier trap type in whichrecombination of a carrier occurs on the phosphorescence dopant, acarrier trap material, and light is emitted from the phosphorescencedopant. However, in each type, it is desired that energy level of thephosphorescence dopant in excited state is lower than that of the hostcompound in excited state.

The phosphorescence dopant can be suitably selected from those commonlyknown, which are used in the light emission layer of an organic ELelement.

The phosphorescence dopant in the present invention is preferably acomplex compound containing a metal belonging to groups 8 to 10 of theperiodic table, and is more preferably an iridium compound, an osmiumcompound, a platinum compound (a platinum complex) or a rare earthcompound, and most preferably an iridium compound.

Specifically listed are compounds described in the following patentpublication. WO 00/70655, Japanese Patent O.P.I. Publication No.2002-280178, Japanese Patent O.P.I. Publication No. 2001-181616,Japanese Patent O.P.I. Publication No. 2002-280179, Japanese PatentO.P.I. Publication No. 2001-181617, Japanese Patent O.P.I. PublicationNo. 2002-280180, Japanese Patent O.P.I. Publication No. 2001-247859,Japanese Patent O.P.I. Publication No. 2002-299060, Japanese PatentO.P.I. Publication No. 2001-313178, Japanese Patent O.P.I. PublicationNo. 2002-302671, Japanese Patent O.P.I. Publication No. 2001-345183,Japanese Patent O.P.I. Publication No. 2002-324679, WO 02/15645,Japanese Patent O.P.I. Publication No. 2002-332291, Japanese PatentO.P.I. Publication No. 2002-50484, Japanese Patent O.P.I. PublicationNo. 2002-322292, Japanese Patent O.P.I. Publication No. 2002-83684,Japanese Patent O.P.I. Publication No. 2002-540572, Japanese PatentO.P.I. Publication No. 2002-117978, Japanese Patent O.P.I. PublicationNo. 2002-338588, Japanese Patent O.P.I. Publication No. 2002-170684,Japanese Patent O.P.I. Publication No. 2002-352960, WO 01/93642,Japanese Patent O.P.I. Publication No. 2002-50483, Japanese PatentO.P.I. Publication No. 2002-100476, Japanese Patent O.P.I. PublicationNo. 2002-173674, Japanese Patent O.P.I. Publication No. 2002-359082,Japanese Patent O.P.I. Publication No. 2002-175884, Japanese PatentO.P.I. Publication No. 2002-363552, Japanese Patent O.P.I. PublicationNo. 2002-184582, Japanese Patent O.P.I. Publication No. 2003-7469,Japanese Patent O.P.I. Publication No. 2002-525808, Japanese PatentO.P.I. Publication No. 2003-7471, Japanese Patent Publication No.2002-525833, Japanese Patent O.P.I. Publication No. 2003-31366, JapanesePatent O.P.I. Publication No. 2002-226495, Japanese Patent O.P.I.Publication No. 2002-234894, Japanese Patent O.P.I. Publication No.2002-235076, Japanese Patent O.P.I. Publication No, 2002-241751,Japanese Patent O.P.I. Publication No. 2001-319779, Japanese PatentO.P.I. Publication No. 2001-319780, Japanese Patent O.P.I. PublicationNo. 2002-62824, Japanese Patent O.P.I. Publication No. 2002-100474,Japanese Patent O.P.I. Publication No. 2002-203679, Japanese PatentO.P.I. Publication No. 2002-343572, and Japanese Patent O.P.I.Publication No. 2002-203678.

Specific examples of compounds used as the commonly knownphosphorescence dopant are shown below, but the present invention is notlimited thereto. In addition, these compounds are possible to besynthesized by the method described in Inorg. Chem. Vol. 40, 1704-1711.

{Fluorescence Dopant (Referred to Also as a Fluorescent Compound)}

Examples of the fluorescence dopant (fluorescent compound) include acoumarin based dye, a pyran based dye, a cyanine based dye, a chloconiumbased dye, a squarylium based dye, an oxobenzanthracene based dye, afluorescene based dye, a rhodamine based dye, a pyrylium based dye, aperylene based dye, a stilbene based dye, a polythiophene based dye, andrare earth complex based phosphor.

Next, an injection layer, a blocking layer, and an electron transportlayer used in the constituent layer of the organic EL element of thepresent invention will be described.

<<Injection Layer: Electron Injection Layer and Hole Injection Layer>>

The injection layer is optionally provided, for example, an electroninjection layer or a hole injection layer, and may be provided betweenthe anode and the light emission layer or hole transport layer, andbetween the cathode and the light emission layer or electron transportlayer as described above.

The injection layer herein means a layer provided between the electrodeand an organic layer in order to reduce the driving voltage or toimprove of light emission efficiency, which is detailed in “ElectrodeMaterial”, Div. 2 Chapter 2, pp. 123-166 of “Organic EL element and itsfrontier of industrialization” (published by NTS Corporation, Nov. 30,1998). As the injection layer, there are a hole injection layer (anodebuffer layer) and an electron injection layer (cathode buffer layer).

The anode buffer layer (hole injection layer) is described in JapanesePatent O.P.I. Publication Nos. 9-45479, 9-260062, and 8-288069, andexamples thereof include a phthalocyanine buffer layer represented by acopper phthalocyanine layer, an oxide buffer layer represented by avanadium oxide layer, an amorphous carbon buffer layer, a polymer bufferlayer employing a conductive polymer such as polyaniline (emeraldine) orpolythiophene.

The cathode buffer layer (electron injection layer) is described indetail in Japanese Patent O.P.I. Publication Nos. 6-325871, 9-17574, and10-74586, and examples thereof include a metal buffer layer representedby a strontium or aluminum layer, an alkali metal compound buffer layerrepresented by a lithium fluoride layer, an alkali earth metal compoundbuffer layer typified by a magnesium fluoride layer, and an oxide bufferlayer typified by an aluminum oxide. The buffer layer (injection layer)is preferably very thin and has a thickness of preferably from 0.1 nm to5 μm depending on kinds of the material used.

<<Blocking Layer: Hole Blocking Layer and Electron Blocking Layer>>

The blocking layer is a layer provided if desired in addition to thefundamental constituent layer as described above, and is, for example, ahole blocking layer as described in Japanese Patent O.P.I. PublicationNos. 11-204258, and 11-204359, and on page 237 of “Organic EL elementand its frontier of industrialization” (published by NTS Corporation,Nov. 30, 1998).

The hole blocking layer is an electron transport layer in a broad sense,and is comprised of material having ability of transporting electronsbut extremely poor ability of holes, which can increase recombinationprobability of electrons and holes by transporting electrons andblocking holes.

Further, the constitution of an electron transport layer described latercan be used in the hole blocking layer in the present invention, ifdesired.

The hole blocking layer in the organic EL element of the presentinvention is preferably provided so as to be in contact with a lightemission layer.

It is preferred that the hole blocking layer contains an azacarbazolederivative as the foregoing host compound.

Further, in the present invention, when there are a plurality of lightemission layers which emit a plurality of different color lights, it ispreferable that a light emission layer emitting light having emissionmaximum in the shortest wavelength of all the light emission layers isprovided closest to the anode. In such a ease, it is preferred that ahole blocking layer is additionally provided between the light emissionlayer emitting a light having emission maximum in the shortestwavelength and a light emission layer provided closest to the anodeexcluding the above light emission layer emitting a light havingemission maximum in the shortest wavelength.

Further, it is preferred that at least 50% by weight of compounds, whichare incorporated in the hole blocking layer arranged in the abovelocation, have an ionization potential 0.3 eV higher than that of thehost compound contained in the light emission layer emitting a lighthaving emission maximum in the shortest wavelength.

Ionization potential is defined as energy required to transfer anelectron in an HOMO (highest occupied molecular orbital) level to thevacuum level, and can be determined by the methods described below.

(I) The ionization potential can be determined via calculation byperforming structural optimization employing Gaussian 98 (Gaussian 98,Revision A. 11.4, M J. Frisch, et al., Gaussian, Inc., Pittsburgh Pa.,2002), which is a software for molecular orbital calculation ofGaussian, Inc., and B3LYP/6-31G* as a key word, and the calculated value(being the value in terms of eV unit) is rounded off at the seconddecimal place. Background in which the calculated value above iseffective is that the calculated value obtained by the above method andexperimental values exhibit high correlation.

(2) It is also possible to obtain ionization potential via a directmeasurement method employing a photoelectron spectroscopy. For example,it is possible to appropriately employ a low energy electronspectrometer “Model AC-1”, produced by Riken Keiki Co., Ltd., or amethod known as ultraviolet photoelectron spectroscopy.

On the other hand, the electron blocking layer is a hole transport layerin a broad sense, and is comprised of material having ability oftransporting holes but extremely poor ability of electrons, which canincrease recombination probability of electrons and holes bytransporting holes and blocking electrons.

The constitution of the hole transport layer as described later can beused as that of the electron blocking layer. The thickness of the holeblocking layer or electron transport layer is preferably 3-100 nm, andmore preferably 5-30 nm.

<<Hole Transport Layer>>

The hole transport layer is comprised of a hole transport materialhaving ability of transporting holes, and a hole injection layer and anelectron blocking layer are included in the hole transport layer in abroad sense. The hole transport layer may be provided as a single layeror plural layers.

The hole transport material has hole injecting ability, holetransporting ability or ability to form a barrier to electrons, and maybe either an organic substance or an inorganic substance. Examplesthereof include a triazole derivative, an oxadiazole derivative, animidazole derivative, a polyarylalkane derivative, a pyrazolinederivative and a pyrazolone derivative, a phenylenediamine derivative,an arylamine derivative, an amino substituted chalcone derivative, anoxazole derivative, a styryl anthracene derivative, a fluorenonederivative, a hydrazone derivative, a stilbene derivative, a silazanederivative, an aniline copolymer, and a conductive oligomer,particularly a thiophene oligomer.

As the hole transport material, those described above are used, but aporphyrin compound, an aromatic tertiary amine compound, or astyrylamine compound is preferably used, and an aromatic tertiary aminecompound is more preferably used.

Typical examples of the aromatic tertiary amine compound and styrylaminecompound include N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl,N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 2,2′-bis(4-di-p-tolylaminophenyl)propane,1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,N,N,N′,N′-tetra-p-tolyl-4,4′-diaminobiphenyl,1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane,bis(4-dimethylamino-2-methylphenyl)-phenylmethane,bis(4-di-p-tolylaminophenyl)phenylmethane,N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′-diaminobiphenyl,N,N,N′,N′-tetraphenyl-4,4′-diaminodiphenyl ether,4,4′-bis(diphenylamino)quardriphenyl, N,N,N-tri(p-tolyl)amine,4-(di-p-tolylamino)-4′-[4-(di-p-tolylamino)styryl]stilbene,4-N,N-diphenylamino(2-diphenylvinyl)benzene,3-methoxy-4′-N,N-diphenylaminostylbenzene, N-phenylcarbazole, compoundsdescribed in U.S. Pat. No. 5,061,569 which have two condensed aromaticrings in the molecule thereof such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD), and compoundsdescribed in Japanese Patent Publication No. 4-308688 such as4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]-triphenylamine (MTDATA)in which three triphenylamine units are bonded in a starburst form.

A polymer in which the material mentioned above is introduced in thepolymer chain or a polymer having the material as the polymer main chaincan be also used. As the hole injection material or the hole transportmaterial, inorganic compounds such as p-type-Si and p-type-SiC areusable.

So-called p-type hole transport materials as disclosed in JapanesePatent O.P.I. Publication No. 11-251067 or described in the literatureof J. Huang et al. (Applied Physics Letters 80 (2002), p. 139) are alsoapplicable. In the present invention, these materials are preferablyused since an emitting element exhibiting a higher efficiency isobtained.

The hole transport layer can be formed by layering the hole transportmaterial by a commonly known method such as a vacuum evaporation method,a spin coating method, a cast method, an inkjet method, and an LBmethod. The thickness of the hole transport layer is not specificallylimited, but is conventionally 5 nm-5 μm, and preferably 5-200 nm. Thehole transport layer may be composed of a single layer structurecomprising one kind or at lest two kinds of the materials mentionedabove.

A positive hole transport layer having a high p-type property doped withimpurity can be utilized. Examples thereof include those described inJapanese Patent O.P.I. Publication Nos. 4-297076, 2000-196140 and2001-102175, and J. Appl. Phys., 95, 5773 (2004).

It is preferable in the present invention to employ such a positive holetransport layer having a high p-type property, since an element withlower power consumption can be prepared.

<<Electron Transporting Layer>>

The electron transport layer comprises a material (electron transportmaterial) having electron transporting ability, and in a broad senserefers to an electron injection layer or a hole blocking layer. Theelectron transport layer can be provided as a single layer or plurallayers.

An electron transport material (which serves also as a hole blockingmaterial) used in a single electron transport layer or in the electrontransport layer closest to the cathode of plural electron transportinglayers has a function of incorporating electrons injected from a cathodeto a light emission layer, and can be selected from commonly knowncompounds. Examples thereof include a nitro-substituted fluorenederivative, a diphenylquinone derivative, a thiopyran dioxidederivative, a carbodiimide, a fluolenylidenemethane derivative, ananthraquinodimethane, an anthrone derivative, and an oxadiazolederivative.

Moreover, a thiadiazole derivative which is formed by substituting theoxygen atom in the oxadiazole ring of the foregoing oxadiazolederivative with a sulfur atom, and a quinoxaline derivative having aquinoxaline ring known as an electron withdrawing group are usable asthe electron transport material. A polymer in which the materialmentioned above is introduced in the polymer side chain or a polymerhaving the material as the polymer main chain can also be used.

A metal complex of an 8-quinolynol derivative such as aluminumtris-(8-quinolynol) (Alq₃), aluminum tris-(5,7-dichloro-8-quinolynol),aluminum tris-(5,7-dibromo-8-quinolynol), aluminumtris-(2-methyl-8-quinolynol), aluminum tris-(5-methyl-8-quinolynol), orzinc bis-(8-quinolynol) (Znq₂), and a metal complex formed by replacingthe central metal of the foregoing complexes with another metal atomsuch as In, Mg, Cu, Ca, Sn, Ga or Pb, can be used as the electrontransport material.

Furthermore, a metal-free or metal-containing phthalocyanine, and aderivative thereof, in which the molecular terminal is replaced by asubstituent such as an alkyl group or a sulfonic acid group, are alsopreferably used as the electron transport material. The distyrylpyrazinederivative exemplified as a material for the light emission layer maypreferably be employed as the electron transport material. An inorganicsemiconductor such as n-type-Si and n-type-SiC may also be used as theelectron transport material in the same manner as in the hole injectionlayer or in the hole transport layer.

The electron transport layer can be formed employing the above-describedelectron transport materials and a known method such as a vacuumevaporation method, a spin coating method, a cast method, a printingmethod including an inkjet method or an LB method. The thickness of theelectron transport layer is not specifically limited, but isconventionally 5 nm-5 μm, and preferably 5-200 nm. The electrontransport layer may be composed of a single layer comprising one kind orat least two kinds of the electron transport material.

An electron transport layer having a high n property doped with impuritycan be utilized. Examples thereof include those described in JapanesePatent O.P.I. Publication Nos. 4-297076, 10-270172, 2000-196140,2001-102175, and J. Appl. Phys., 95, 5773 (2004).

It is preferred in the present invention that use of such an electrontransport layer having a high n property can provide an element withlower power consumption.

<<Anode>>

For the anode of the organic EL element, a metal, an alloy, or aconductive compound each having a high working function (4 eV or more),and mixture thereof are preferably used as the electrode material.Specific examples of such an electrode material include a metal such asAu, and a transparent conductive material such as CuI, indium tin oxide(ITO), SnO₂ or ZnO.

A material such as IDIXO (In₂O₃—ZnO) capable of forming an amorphous andtransparent conductive layer may be used. The anode may be prepared byforming a thin layer of the electrode material according to aevaporation or sputtering method, and by forming the layer into adesired pattern according to a photolithographic method. When precisionof the pattern is not desired to be not so high (roughly 100 μm ormore), the pattern may be formed via evaporation or sputtering of theelectrode material through a mask having a desired form.

When a coatable material such as an organic conductive compound is used,a wet coating method such as a printing method or a coating method canbe used. When light is emitted through the anode, transmittance of theanode is preferably 10% or more, and the sheet resistance of the anodeis preferably several hundreds Ω/□ or less. The thickness of the layeris conventionally 10-1000 nm, and preferably 10-200 nm, depending onkinds of materials used.

<<Cathode>>

On the other hand, for the cathode, a metal (referred to also as anelectron injecting metal), an alloy and a conductive compound eachhaving a low working function (4 eV or less), and a mixture thereof isused as the electrode material.

Specific examples of such an electrode material include sodium, asodium-potassium alloy, magnesium, lithium, a magnesium/copper mixture,a magnesium/silver mixture, a magnesium/aluminum mixture, amagnesium/indium mixture, an aluminum/aluminum oxide (Al₂O₃) mixture,indium, a lithium/aluminum mixture, and a rare-earth metal.

Among them, a mixture of an electron injecting metal and a metal higherin the working function than that of the electron injecting metal, suchas a magnesium/silver mixture, a magnesium/aluminum mixture, amagnesium/indium mixture, an aluminum/aluminum oxide (Al₂O₃) mixture, alithium/aluminum mixture, or aluminum is suitable in view of durabilityagainst electron injection and oxidation.

The cathode can be prepared forming a thin layer of such an electrodematerial by a method such as a deposition or sputtering method. Thesheet resistance as the cathode is preferably several hundreds Ω/□ orless, and the thickness of the layer is conventionally 10 nm-5 μm, andpreferably 50-200 nm.

It is preferred in increasing emission luminance that either the anodeor the cathode of the organic EL element, through which light passes, istransparent or semi-transparent.

After a layer of the metal described above as a cathode is formed togive a thickness of 1-20 nm, the transparent conductive material asdescribed in the anode is layered thereon, whereby a transparent orsemi-transparent cathode can be prepared. Employing this cathode, anelement can be manufactured in which both anode and cathode aretransparent.

<<Supporting Substrate>>

The supporting substrate (referred to also as a base body, a substrate,a base material or a support) employed for the organic EL element of thepresent invention is not limited to specific kinds of materials such asglass and plastic, as long as it is transparent. When light is taken outfrom the side of a substrate, the substrate is preferably transparent.Preferable examples of the usable substrate include glass, quartz and atransparent resin film. Specifically preferred supporting substrate is aresin film capable of providing flexibility to the organic EL element.

Examples of materials for the resin film include polyesters such aspolyethylene terephthalate (PET) and polyethylene naphthalate (PEN),polyethylene, polypropylene, cellophane, cellulose esters and theirderivatives such as cellulose diacetate, cellulose triacetate, celluloseacetate butylate, cellulose acetate propionate (CAP), cellulose acetatephthalate (TAC), and cellulose nitrate, polyvinylidene chloride,polyvinylalcohol, polyethylenevinylalcohol, syndiotactic polystyrene,polycarbonate, norbornane resin, polymethylpentene, polyetherketone,polyimide, polyether sulfone (PES), polyphenylene sulfide, polysulfones,polyether imide, polyetherketone imide, polyimide, fluorine resin,nylon, polymethyl methacrylate, acryl or polyarylates, and cyclo-olefinresins such as ARTON (commercial name, manufactured by JSR Corp.) orAPEL (commercial name, manufactured by Mitsui Chemicals Inc.).

On the surface of the resin film, an inorganic or organic cover film ora hybrid cover film comprising the both may be formed, and the coverfilm is preferably one with a barrier ability having a water vaporpermeability of 0.01 g/(m²·24 h) or less (at 25±0.5° C. and at (90±2) %RH), measured by a method in accordance with JIS K 7129-1992, and ismore preferably one with a high barrier ability having an oxygenpermeability of 10⁻³ mL/(m²·24 hr·MPa) or less as well as a water vaporpermeability of 10⁻⁵ g/(m²·24 h) or less, measured by a method inaccordance with JIS K 7126-1987.

Any materials capable of preventing penetration substances such asmoisture and oxygen causing degradation of the element are usable forforming the bather film, and for example, silicon oxide, silicon dioxideand silicon nitride are usable. It is more preferred that the barrierfilm has a multi-layered structure composed of a layer of the inorganicmaterial and a layer of an organic material for improving fragility ofthe film. It is preferred that the both layers are alternativelylaminated several times though there is no limitation as to thelamination order of the inorganic layer and the organic layer.

The method to form the barrier film is not specifically limited, and forexample, a vacuum evaporation method, a sputtering method, a reactionsputtering method, a molecular beam epitaxy method, a cluster ion beammethod, an ion plating method, a plasma polymerization method, anatmospheric pressure plasma polymerization method, a plasma CVD method,a laser CVD method, a heat CVD method and a coating method areapplicable, and the atmospheric pressure plasma polymerization method asdescribed in Japanese Patent O.P.I. Publication No. 2004-68143 isspecifically preferable.

As the opaque supporting substrate, for example, a metal plate such asan aluminum plate and a stainless steel plate, a film or an opaque resinsubstrate and a ceramic substrate are cited.

The taking-out efficiency of light emission of an organic EL element ofthe present invention at room temperature is preferably 1% or more, andmore preferably 5% or more.

Herein, taking-out quantum yield (%) is as follows. Taking-out quantumyield (%)=(the number of photons emitted to the exterior of the organicelectroluminescent element×100)/(the number of electrons supplied to theorganic electroluminescent element)

A hue-improving filter such as a color filter may be used in combinationor a color conversion filter which can convert from emission light colorfrom an organic EL element to multi-color employing a phosphor may beused in combination. In cases where the color conversion filter, theλmax of light emitted from the organic EL element is preferably 480 nmor less.

<<Sealing>>

As the sealing means used in the present invention, there is a method inwhich adhesion of a sealing member to an electrode and a supportingsubstrate is carried out employing an adhesive agent.

The sealing member is formed so as to cover the displaying region of anorganic EL element and may have a flat plate shape or a concave plateshape, and transparency and an electrical insulation property thereofare not specifically limited.

Specific examples of the sealing member include a glass plate, a polymerplate, a polymer film, a metal plate and a metal film. As the glassplate, a plate of soda-lime glass, barium strontium-containing glass,lead glass, aluminosilicate glass, boron silicate glass, barium boronsilicate glass or quartz is usable.

As the polymer plate, a plate of polycarbonate, acryl resin,polyethylene terephthalate, polyether sulfide or polysulfone is usable.As the metal plate, a plate composed of one or more kinds of metalsselected from the group consisting of stainless steel, iron, copper,aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum,silicon, germanium and tantalum, and alloys thereof is provided.

In the present invention, the polymer film and the metal film arepreferably used since the element formed from a thinner film can beprepared.

The polymer film is preferably one having an oxygen permeability of1×10⁻³ mL/(m²·24 hr·MPa) or less, measured by a method in accordancewith JIS K 7126-1987, and a water vapor permeability {at 25±0.5° C. andat (90±2) % RH} of 1×10⁻³ g/(m²·24 h) or less, measured by a method inaccordance with JIS K 7129-1992.

For processing the sealing material in the form of the concave, asandblast treatment and a chemical etching treatment are used.

As the adhesive agent, there are mentioned a photo-curable orthereto-curable adhesive agent containing a reactive vinyl group such asan acrylic acid based oligomer or a methacrylic acid based oligomer, anda moisture curable adhesive agent such as 2-cyanoacrylate. Examples ofthe adhesive agent include an epoxy based thermally and chemically (twoliquid type) curable adhesive agents, a hot-melt type polyamide,polyester or polyolefin adhesive agents, and a cationic curable typeUV-curable epoxy adhesive.

The organic EL element is degraded by a heat treatment in some cases,and therefore, an adhesive agent capable of being cured within thetemperature range of from room temperature to 80° C. is preferred. Adrying agent may be dispersed in the adhesive agent. Coating of theadhesive agent onto the adhering portion may be performed by a dispenseravailable on the market or by printing such as screen printing.

It is preferred that a layer made of an inorganic or organic material isformed as a sealing layer on an electrode placed on the side facing asupporting substrate an organic layer provided between the substrate andthe electrode, so as to cover the electrode and the organic layer andcontact with the substrate. In such a case, a material to form thesealing layer may be a material having a function to inhibit permeationsubstances such as water and oxygen causing degradation of the element,and for example, silicon oxide, silicon dioxide and silicon nitride areusable.

The sealing layer preferably has a multi-layered structure composed of alayer made of an inorganic material and a layer made of an organicmaterial to improve fragility of the layer. The method of forming thelayer is not specifically limited, and for example, a vacuum evaporationmethod, a sputtering method, a reaction sputtering method, a molecularbeam epitaxy method, a cluster-ion beam method, an ion plating method, aplasma polymerization method, an atmospheric pressure plasmapolymerization method, a plasma CVD method, a laser CVD method, a heatCVD method and a coating method are applicable.

In the spacing between the sealing layer and the displaying portion ofthe organic EL element, an inactive gas such as nitrogen or argon or aninactive liquid such as fluorinated hydrocarbon or silicone oil ispreferably injected in the form of gas or liquid phase. It is alsopossible that vacuum is provided in the spacing. A hygroscopic compoundcan also be enclosed inside.

Examples of the hygroscopic compound include metal oxide such as sodiumoxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide oraluminum oxide; sulfate such as sodium sulfate, calcium sulfate,magnesium sulfate or cobalt sulfate; metal halide such as calciumchloride, magnesium chloride, cesium fluoride, tantalum fluoride, ceriumbromide, magnesium bromide, barium iodide or magnesium iodide; andperchlorate such as barium perchlorate or magnesium perchlorate.Anhydride of the sulfate, halide and perchlorate is preferably usable.

<<Protective Layer and Protective Plate>>

A protective layer or a protective plate may be provided on theforegoing sealing layer formed on the side facing the substrate throughthe organic layer or outside the sealing layer in order to raisemechanical strength of the element. Specifically when sealing is carriedout by the sealing layer as described above, such a protective layer orplate is preferably provided, since strength of the element is not sohigh. As materials for the protective layer or plate, the same glassplate, polymer plate, polymer film, metal plate and metal film as thosedescribed above to be used for sealing are usable. The polymer film ispreferably used from the viewpoint of light weight and a thin layerformation property.

<<Taking-Out of Light>>

It is generally said that, in the organic EL element, light is emittedin a layer whose refractive index (the refractive index is about1.7-2.1) is higher than that of air, and only 15 to 20% of the lightemitted in the light emission layer can be taken out. This is becauselight which enters a boundary (a boundary between a transparentsubstrate and the atmosphere) at an angle θ larger than a critical angleis totally reflected and cannot be taken out from the element, orbecause light is totally reflected at a boundary between the transparentsubstrate and the transparent electrode or between the transparentsubstrate and the light emission layer, so that the light exits from theside of the element through the transparent electrode or the lightemission layer.

As methods to improve the light taking-out efficiency, there are amethod to form concavity and convexity on the surface of the transparentsubstrate to prevent total internal reflection at a boundary between thetransparent substrate and atmospheric air (see U.S. Pat. No. 4,774,435);a method to provide light focusing properties to the substrate toimprove the efficiency (see Japanese Patent O.P.I. Publication No.63-314795); a method to form a reflection surface on the side of theelement (see Japanese Patent O.P.I. Publication No. 1-220394); a methodto form a flat layer having an intermediate refractive index between thesubstrate and the light emission layer to form an anti-reflection layer(see Japanese Patent O.P.I. Publication No. 62-172691); a method to forma flat layer having a low refractive index between the substrate and thelight emission layer (see Japanese Patent O.P.I. Publication No.2001-202827); and a method to form a diffraction lattice at a boundarybetween any two of the substrate, the transparent electrode and thelight emission layer (including a boundary between the substrate andatmospheric air) (see Japanese Patent O.P.I. Publication No. 11-283751).

In the present invention, these methods can be used in combination withthe organic electroluminescent element of the present invention. Also, amethod of forming a flat layer having a lower refractive index than thatof the substrate between the substrate and the light emission layer, ora method of forming a diffraction lattice at a boundary between any ofthe substrate, transparent electrode and light emission layer (includinga boundary between the substrate and the atmosphere) can be preferablyused.

In the present invention, an element exhibiting further higher luminanceand durability can be obtained by using these methods in combination.

When a low refractive index medium with a thickness greater than lightwavelength is formed between a transparent electrode and a transparentsubstrate, the taking-out efficiency of light, which comes out of thetransparent electrode, increases, as the refractive index of the mediumdecreases.

As a low refractive index layer, aerogel, porous silica, magnesiumfluoride and a fluorine-containing polymer are cited, for example. Sincerefractive index of the transparent substrate is conventionally 1.5-1.7,the refractive index of the low refractive index layer is preferably 1.5or less and more preferably 1.35 or less.

The thickness of a low refractive index medium is preferably twice ormore of the wavelength of light in the medium, because when thickness ofthe low refractive index medium is such that the electromagnetic waveexuding as an evanescent wave enters the transparent substrate, theeffect of the low refractive index layer is reduced.

A method to provide a diffraction lattice at a boundary where the totalinternal reflection occurs or in some of the media has a feature thatthe effect of enhancing the light extraction efficiency increases.

The intension of this method is to provide a diffraction lattice at aboundary between any of the layers or in any of the mediums (in thetransparent substrate or in the transparent electrode) and extract lightwhich cannot exit due to total reflection occurring at a boundarybetween the layers among lights emitted in the light emission layer,which uses the property of the diffraction lattice that can change thedirection of light to a specific direction different from the directionof reflection due to so-called Bragg diffraction such as primarydiffraction or secondary diffraction.

It is preferred that the diffraction lattice to be provided has atwo-dimensional periodic refractive index. This is because, since lightgenerated in the light emission layer is emitted randomly in all thedirections, only the light proceeding in a specific direction can bediffracted when a general one-dimensional diffraction lattice having aperiodic refractive index distribution only in a specific direction isused, which does not greatly increase the light taking-out efficiency.

However, a refractive index distribution is two-dimensionallydistributed, whereby the light proceeding in all the directions can bediffracted, and then the light taking-out efficiency is increased.

The position where the diffraction lattice is introduced, as previouslydescribed, is any of boundaries each between layers or in a medium (inthe transparent substrate or in the transparent electrode), but it ispreferably provided in the vicinity of the organic light emission layerwhere the light is emitted.

In this case, the period of the diffraction lattice is preferably about½ to 3 times the wavelength of light in the medium.

The array of the diffraction lattice is preferably two-dimensionallyrepeated as in the shape of a square lattice, a triangular lattice, or ahoneycomb lattice.

<<Light Collection Sheet>>

In the organic EL element of the present invention, luminance in aspecified direction can be increased, for example, by providing astructure in the form of a micro-lens array on the light taking-out sidesurface of the substrate or in combination with a so-called lightcollection sheet, whereby light is focused in a specific direction, forexample, in the front direction to the light emitting plane of theelement.

As an example of a micro-lens array, there is one in which quadrangularpyramids having a side of 30 μm and having a vertex angle of 90° aretwo-dimensionally arranged on the light taking-out side surface of thesubstrate. The side of the quadrangular pyramids is preferably 10-100μm. When the length of the side is shorter than the above range, thelight is colored via producing of the effect of diffraction, while whenit is longer than the above range, it becomes unfavorably thick.

As the light collection sheet, one practically applied for an LEDbacklight of a liquid crystal display is applicable. Usable examples ofsuch a sheet include a brightness enhancing film (BEF) produced bySUMITOMO 3M Inc.

As shape of a prism sheet, there may be included one in which atriangle-shaped strip having a vertex angle of 90° and a pitch of 50 μmprovided on a substrate, one having round apexes, one having a randomlychanged pitch or other ones.

In order to control an emission angle of light emitted from the lightemitting element, a light diffusion plate or film may be used incombination with the light collection sheet. For example, a diffusionfilm (Light-Up, produced by KIMOTO Co., Ltd.) is usable.

<<Use of Organic Thin Film Element>>

The organic thin film element of the present invention can be used as anorganic EL element, a display device, a display, or various lightemission sources. Examples of the light emission sources include anilluminating device (a home lamp or a room lamp in a car), a backlightfor a watch or a liquid crystal, a light source for boardingadvertisement, a signal device, a light source for a photo memorymedium, a light source for an electrophotographic copier, a light sourcefor an optical communication instrument, and a light source for anoptical sensor, but the present invention is not limited thereto.Specifically, it is effectively usable as a backlight for a liquidcrystal or a light source for illumination.

Further, in preparation of an organic thin film element of the presentinvention, patterning may be carried out with a metal mask or by aninkjet printing method, if desired. The patterning may be carried outonly in electrodes, in both electrodes and light emission layers, or inall the layers of the element. Further, the element can also be preparedaccording to a commonly known method.

Color of light emitted from the organic EL element of the presentinvention or from the compounds in the present invention is specifiedwith color obtained when measurements determined by a spectral radianceluminance meter CS-1000 (produced by Konica Minolta Sensing Co., Ltd.)are applied to the CIE chromaticity coordinates in FIG. 4.16 on page 108of “Shinpen Shikisai Kagaku Handbook (edited by The Color ScienceAssociation of Japan, University of Tokyo Press, 1985).

When the organic EL element of the present invention is a white lightelement, “white” means that when front luminance of a 2° viewing angleis determined via the above method, chromaticity in the CIE 1931Chromaticity System at 1,000 Cd/m² is in the range of X=0.33±0.07 andY=0.33±0.1.

<<Illuminating Device>>

An illuminating device of the present invention will be described. Theilluminating device of the present invention possesses theabove-described organic EL element.

The organic EL element of the present invention may be employed as onehaving a resonator structure. As intended use of the aforesaid organicEL element having such a resonator structure include, provided are alight source for an optical memory medium, a light source for anelectrophotographic copier, a light source for an optical communicationprocessor, and a light source for an optical sensor, but the presentinvention is not limited thereto. Further, laser oscillation may also beapplied for the above-described intended use.

Further, the organic EL element of the present invention may also beemployed as a type of lamp for lighting or an exposure light source, aprojection device to project images, and a display device (display) todirectly visualize still images and moving images. A drive systememployed as a display for reproduction of moving images may be allowedto be a simple matrix (passive matrix) system, and also allowed to be anactive matrix system. Alternatively, it is possible to prepare afull-color display device by using at least two types of the organic ELelements of the present invention having different light emittingcolors,

One example of a display device possessing an organic EL element of thepresent invention, will be described referring to figures.

FIG. 1 is a schematic diagram showing one example of a display devicepossessing an organic EL element. It is a schematic diagram of a displaysuch as a cellular phone display, for example, to display imageinformation via light emission of an organic EL element.

Display 1 is composed of display section A having a plurality of pixelsand control section B to conduct image scanning of display section A,based on image information.

Control section B is electrically connected to display section A;scanning signals and image data signals are transmitted to each of theplural pixels based on the image information from the exterior; andpixels of each scanning line sequentially emit light in response toimage data signals through scanning signals to display image informationon display section A via scanning of images.

FIG. 2 is a schematic diagram of display section A.

Display section A possesses a substrate and provided thereon, a wiringsection possessing plural scanning lines 5 and data lines 6, and pluralpixels 3. The major members of display section A will be describedbelow.

In the figure, shown is the case where light emitted by pixel 3 is takenout in the white arrow direction (in the lower direction).

Each of scanning lines 5 and plural data lines 6 in a wiring section ismade of a conductive material and scanning lines 5; scanning lines 5 andplural data lines 6 are orthogonal in the form of a lattice, and areconnected to pixel 3 (not shown in the figure in detail).

When a scanning signal is applied from scanning line 5, pixel 9 receivesan image data signal from data line 6 to produce luminescence inresponse to the receiving image data. It is possible to display fullcolor by appropriately placing pixels in the red region, pixels in thegreen region and pixels in the blue region in parallel for lightemission colors on the same substrate.

Next, the light emission process will be described.

FIG. 3 shows a schematic diagram of a pixel.

The pixel possesses organic EL element 10, switching transistor 11,drive transistor 12, and condenser 13. As organic EL element 10, red,green and blue light emitting organic EL elements are employed forplural pixels, and these are placed in parallel on the same substrate todisplay full color.

In FIG. 3, image data signals are applied to the drain of switchingtransistor 11 via data line 6 from control section B. Subsequently, whena scanning signal is applied to the gate of switching transistor 11 viascanning line 5 from control section B, the drive of switchingtransistor 11 is activated, and an image data signal applied to thedrain is transmitted to the gate of condenser 13 and drive transistor12.

Through transmission of the image data signal, condenser 13 is chargeddepending on the electrical potential of the image data signal, andsimultaneously, the drive of drive transistor 12 is activated. In drivetransistor 12, the drain is connected to power supply line 7; the sourceis connected to the electrode of organic EL element 10; and electriccurrent is supplied to organic EL element 10 from power supply line 7,depending on the electric potential of the image data signal applied tothe gate.

When a scanning signal is transferred to the following scanning line 5via sequential scanning of control section B, the drive of switchingtransistor 11 is deactivated. However, since condenser 13 maintains theelectrical potential of a charged image data signal even though thedrive of switching transistor 11 is deactivated, the drive of drivetransistor 12 is kept activated, and light emission of organic ELelement 10 is continued until the following scanning signal is applied.When the following scanning signal is applied via sequential scanning,drive transistor 12 is driven depending on the electrical potential ofthe next image data signal synchronized with a scanning signal, wherebyorganic EL element 10 produces luminescence.

That is, as to light emission of organic EL element 10, switchingtransistor 11 and drive transistor 12 as the active element are providedwith respect to organic EL element 10 for each of the plural pixels, andorganic EL element 10 for each of plural pixels 3 produces luminescence.Such the light emitting method is called an active matrix system.

Herein, light emission of organic EL element 10 may be light emissionexhibiting a plurality of gradations obtained via a multi-valued imagedata signal having a plurality of gradation potentials, or may beon-and-off of a prescribed light emitting amount obtained via a binaryimage data signal. Further, the electrical potential of condenser 13 maybe continuously maintained until the next scanning signal is applied, ormay be discharged immediately before the next scanning signal isapplied.

In the present invention, in addition to the above-described activematrix system, may be allowed to be used is a light emission drive of apassive matrix system in which an organic EL element emits light,depending on the data signal, only when a scanning signal is scanned.

FIG. 4 is a schematic diagram of a display device of a passive matrixsystem. In FIG. 4, plural scanning lines 5 and plural image data lines 6sandwiching pixel 3 and facing to each other are provided in the form ofa lattice.

When the scanning signal of scanning lines 5 are applied via sequentialscanning, pixels 3 connected to applied scanning lines 5 emit light inresponse to the image data signal.

In the case of a passive matrix system, pixels 3 have no active element,resulting in reduction of manufacturing cost.

Further, the organic EL material of the present invention can be appliedto an organic EL element substantially emitting white light. A pluralityof light emitting colors are simultaneously emitted from a plurality oflight emitting materials to obtain white light emission via colormixture. A combination with a plurality of light emitting colors may beone including three light emission maximum wavelengths of the threeprimary colors of blue, green and red, or maybe one including two lightemission maximum wavelengths utilizing the complementary colorrelationship such as blue and yellow or bluish-green and orange.

EXAMPLE

Next, the present invention will be described referring to Examples, butthe present invention is not limited thereto. In addition, compoundsused in Examples are shown below.

Example 1 Preparation of Organic EL Element <<Preparation of CoatingSolutions 1-1 to 1-8>>

Under nitrogen atmosphere, 600 mg of 1-2a prepared in the foregoingsynthetic example and 30 mg of Ir-1 were dissolved in dehydrateddichloroethane, while stirring and exposed to UV rays employing a highpressure mercury lamp for 120 seconds to obtain coating solution 1-1.

Coating solutions 1-2 to 1-8 were prepared similarly to preparation ofcoating solution 1-1, except that compound 1-2a was replaced bycompounds shown in Table 1.

It was possible to be confirmed that a polymer had been prepared fromthe monomer contained therein by analyzing a part of each of coatingsolutions 1-1 to 1-8 employing a commercially available LC-Mass.

<<Preparation of Organic EL Element 1-1>>

A substrate (NA45, produced by NH Techno Glass Corp.), prepared byforming a 100 nm thick ITO (indium tin oxide) film as an anode on aglass plate having a size of 100×100×1.1 min, was subjected topatterning, and a transparent supporting substrate provided with thisITO transparent electrode was cleaned with isopropyl alcohol viaultrasonic waves, followed by being dried employing dry nitrogen gas andbeing cleaned for 5 minutes employing UV ozone.

This substrate was placed on a spin coater, and a solution prepared bydiluting poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate(PEDOT/PSS, produced by Bayer Co., BAYTRON P A1 4083) by 70% with purewater was coated by a spin coating method to form a film at 3,000 rpmfor 30 seconds, followed by drying at 200° C. for one hour, resulting information of a hole transport layer having a film thickness of 30 nm.

After completing a drying treatment, a substrate was placed on the spincoater again, and coating solution 1-1 was spin-coated at 1000 rpm for30 seconds, so as to give a film thickness of 40 mm, followed by dryingin vacuum at 60° C. for one hour to obtain a light emission layer.

Next, this substrate was fixed on a substrate holder in a vacuumevaporator, and inside the vacuum evaporator, 200 mg of bathocuproine(BCP) were charged in a molybdenum resistance heating boat; 200 mg ofAlq₃ were charged in another molybdenum resistance heating boat. Afterdepressurizing the vacuum chamber to 4×10⁻⁴ Pa, the foregoing heatingboat in which BCP was charged was heated via electricity application toconduct evaporation on the foregoing light emission layer at adeposition rate of 0.1 nm/sec, and a hole blocking layer having a filmthickness of 10 nm was further provided.

Subsequently, the foregoing heating boat in which Alq₃ was charged washeated via electricity application, and evaporation was conducted on theforegoing hole blocking layer at a deposition rate of 0.1 nm/sec tofurther form an electron transport layer having a film thickness of 40nm. In addition, the substrate temperature during evaporation was roomtemperature.

Subsequently, lithium fluoride and aluminum were deposited so as to givethicknesses of 0.5 nm and 110 nm, respectively to form a cathode. Thus,organic EL element 1-1 was prepared.

<<Preparation of Organic EL Elements 1-2 to 1-8>>

Organic EL elements 1-2 to 1-8 were prepared similarly to preparation oforganic EL element 1-1, except that coating solution 1-1 was replaced bycoating solutions 1-2 to 1-8, respectively.

<<Evaluation of Organic EL Elements 1-1 to 1-8>>

The resulting organic EL elements 1-1 to 1-8 were evaluated as shownbelow.

<<Externally Taking-Out Quantum Efficiency>>

The externally taking-out quantum efficiency (%) of each of theresulting organic EL elements 1-1 to 1-8 during application of aconstant current of 2.5 mA/cm² under dried nitrogen atmosphere wasmeasured, and shown in Table 1. In addition, a spectrum radiationluminance meter CS-1000, manufactured by Konica Minolta Sensing, Inc.,was employed for the measurements.

The measured results of the externally taking-out quantum efficiencyshown in Table 1 are represented by the relative value when the measuredvalue of organic EL element 1-1 is set to 100.

<<Light Emission Lifetime>>

Time necessary for reducing luminance to half of the luminanceimmediately after emission at the initial time (initial luminance) wasmeasured when driving with a constant current of 2.5 mA/cm², and wasdesignated as a measure of half-lifetime (τ^(0.5)).

A spectrum radiation luminance meter CS-1000, manufactured by KonicaMinolta Sensing, Inc., was employed for the measurements.

The measured results of the light emission lifetime shown in Table 1 arerepresented by the relative value when the measured value of organic ELelement 1-1 is set to 100.

Obtained results are shown in Table 1.

TABLE 1 Externally taking-out Light Host compound quantum emissionElement (Purity) efficiency lifetime Remarks 1-1 1-2a (99.30%) 100 100Comparative example 1-2 1-2b (98.02%) 106 113 Comparative example 1-31-2c (99.53%) 112 182 Comparative example 1-4 1-2d (99.92%) 126 245Present invention 1-5 1-2e (99.99%) 132 388 Present invention 1-6 1-1(99.98%) 122 353 Present invention 1-7 1-12 (99.99%) 142 398 Presentinvention 1-8 1-19 (99.99%) 138 402 Present invention

As is clear from Table 1, organic EL elements of the present inventionexhibit longer light emission lifetime in comparison to organic ELelements in Comparative examples.

Example 2 Preparation of Organic EL Element (Preparation of CoatingSolutions 2-1A to 2-3A)

The following coating solutions 2-1A to 2-3A were prepared employing thecompound shown in Table 2.

Under nitrogen atmosphere, 600 mg of exemplified compound 4-1a (a puritycontent of 98.85% by weight) were dissolved in 60 mL of dehydratedxylene, and heated at 130° C. for 30 minutes to prepare coating solution2-1A.

Subsequently, under nitrogen atmosphere, 600 mg of exemplified compound1-21a (a purity content of 98.23% by weight) and 30 mg of exemplifiedcompound 2-25a (a purity content of 99.31% by weight) were dissolved in60 mL of dehydrated xylene, and heated at 130° C. for 30 minutes toprepare coating solution 2-2A.

Further, under nitrogen atmosphere, 600 mg of exemplified compound 3-14a(a purity content of 99.18% by weight) were dissolved in 60 mL ofdehydrated xylene, and heated at 130° C. for 30 minutes to preparecoating solution 2-3A.

(Preparation of Coating Solutions 2-1B to 2-3B)

Coating solutions 2-1B to 2-3B were prepared similarly to preparation ofcoating solutions 2-1A to 2-3A, by utilizing materials shown in Table 2.

It was possible to be confirmed that a polymer had been prepared fromthe monomer contained therein by analyzing a part of each coatingsolution employing a commercially available LC-Mass.

<<Preparation of Organic EL Element 2-1>>

A substrate (NA45, produced by NH Techno Glass Corp.), prepared byforming a 100 nm thick ITO (indium tin oxide) film as an anode on aglass plate having a size of 100×100×1.1 mm, was subjected topatterning, and a transparent supporting substrate provided with thisITO transparent electrode was cleaned with isopropyl alcohol viaultrasonic waves, followed by being dried employing dry nitrogen gas andbeing cleaned for 5 minutes employing UV ozone.

This substrate was placed on a spin coater, and a solution prepared bydiluting poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate(PEDOT/PSS, produced by Bayer Co., BAYTRON P A1 4083) by 70% with purewater was coated by a spin coating method to form a film at 3,000 rpmfor 30 seconds, followed by drying at 200° C. for one hour, resulting information of a hole injection layer having a film thickness of 30 nm.

After completing a drying treatment, a substrate was placed on the spincoater again, and coating solution 2-1A was spin-coated at 1000 rpm for30 seconds to form a hole transport layer. Subsequently, coatingsolution 2-2A was spin-coated at 1000 rpm for 30 seconds to form a lightemission layer, and further, coating solution 2-3A was spin-coated at1000 rpm for 30 seconds to form an electron transport layer.

Next, this substrate was fixed on a substrate holder in a vacuumevaporator, and inside the vacuum evaporator, 200 mg of Alq₃ werecharged in a molybdenum resistance heating boat.

After depressurizing the vacuum chamber to 4×10⁻⁴ Pa, the foregoingheating boat in which Alq_(a) was charged was heated via electricityapplication to conduct evaporation on the foregoing electron transportlayer at a deposition rate of 0.1 nm/sec, and an electron injectionlayer having a film thickness of 40 nm was further provided. In additionthe substrate temperature during evaporation was mom temperature.

Subsequently, lithium fluoride and aluminum were deposited so as to givethicknesses of 0.5 nm and 110 nm, respectively to form a cathode. Thus,organic EL element 2-1 was prepared.

(Preparation of Organic EL Element 2-2)

Organic EL element 2-2 was prepared similarly to preparation of organicEL element 2-1A, by utilizing coating solutions 2-1B, 2-2B, and 2-3B.

When electricity was applied to these elements, light emission of bluecolor was obtained, whereby it was confirmed that these elements wereusable as an organic EL display.

<<Evaluation of Organic EL Elements 2-1 and 2-2>>

Similarly to the evaluation of organic EL element 1-1 in Example 1,results shown in Table 2 were obtained. In addition, the measuredresults of the light emission lifetime shown in Table 2 are representedby the relative value when the measured value of organic EL element 2-1is set to 100.

TABLE 2 Hole transport Light emitting Electron transport Light materialmaterial material emission Element Purity (%) Purity (%) Purity (%)lifetime Remarks 2-1 4-1a 1-21a (98.23%)/ 3-14a (99.18%) 100 Comparative(98.85%) 2-25a (99.31%) example 2-2 4-1b 1-21b (99.99%)/ 3-14b (99.99%)402 Present (99.99%) 2-25b (99.99%) invention

As is clear from Table 2, the organic EL element of the presentinvention exhibits longer light emission lifetime in comparison to theorganic EL elements in Comparative example.

Example 3 Preparation of Organic EL Element 3-1 Preparation ofWhite-Illuminating Device

Organic EL element 3-1 was prepared similarly to preparation of organicEL element 1-1, except that 30 mg of dopant compound Ir-1 contained in alight emission layer was replaced by 9 mg of Ir-1, 9 mg of Ir-9 and 12mg of Ir-14 in preparation of organic EL element 1-5 in Example 1.

When electricity was applied to this element, while light was obtained,and it was confirmed that the element was usable as an illuminatingdevice.

Example 4 Synthesis of Compound 5-1a Comparative OrganicElectroluminescent Element Material

In 200 mL of toluene, dissolved were 15.0 g of compound 5-1-1 (HPLCpurity of 99.65%) and 18.0 g of compound 5-1-2 (HPLC purity of 99.82%),followed by addition of 1.0 g of Aliquat 336 and 30 mL of a 2 mol/Lsodium hydrogen carbonate solution under nitrogen atmosphere.

After vigorously stirring this mixture, and heating it via reflow for 20hours, 1 g of bromobenzene was added, followed by heating for 5 hours.This reaction solution was cooled to 60° C., and slowly added in a mixedsolution of 3 L of methanol and 300 mL of pure water while stirring.

A precipitate was filtrated and repeatedly washed with methanol and purewater, and subsequently dried in a vacuum oven at 60° C. for 10 hours toobtain 19.0 g of compound 5-1a as a comparative organicelectroluminescent element material. Spectral characteristics ofcompound 5-1a coincided with those of compound 5-1.

Synthesis of Compound 5-1b Organic Electroluminescent Element Materialof the Present Invention

Nineteen grams of compound 5-1b as an organic electroluminescent elementmaterial of the present invention were prepared similarly to synthesisof compound 5-1a as a comparative organic electroluminescent elementmaterial, except that employed were 5-1-1 (HPLC purity of 99.99%) and5-1-2 (HPLC purity of 99.99%) each as a high purity monomer having animpurity content of 1000 ppm or less.

Preparation of Organic EL Element 5-1 Comparative Example

A substrate (NA45, produced by NH Techno Glass Corp.), prepared byforming a 150 nm thick ITO (indium tin oxide) film as an anode on aglass plate, was subjected to patterning, and a transparent supportingsubstrate provided with this ITO transparent electrode was cleaned withisopropyl alcohol via ultrasonic waves, followed by being driedemploying thy nitrogen gas and being cleaned for 5 minutes employing UVozone.

This substrate was moved in nitrogen atmosphere, and a solution in which60 mg of compound 5-1a as a comparative organic EL element material weredissolved in 6 mL of toluene was coated by a spin coating method to forma film at 1,000 rpm for 30 seconds, followed by drying in vacuum at 150°C. for one hour to form a hole transport layer having a film thicknessof 30 nm.

Subsequently, a solution in which 60 mg of H1 and 6.0 mg of Ir-12 weredissolved in 6 mL of toluene was coated on the hole transport layer by aspin coating method to form a film at 1,000 rpm for 30 seconds, followedby heating in vacuum at 150° C. for one hour to obtain a light emissionlayer having a film thickness of 40 nm.

Further, a solution in which 20 mg were dissolved in 6 mL of butanol wascoated by a spin coating method to form a film at 1,000 rpm for 30seconds, followed by heating in vacuum at 150° C. for one hour to obtainthe first electron transport layer having a film thickness of 20 nm.

Next, this substrate was fixed on a substrate holder in a vacuumevaporator, and inside the vacuum evaporator, 200 mg of Alq₃ werecharged in a molybdenum resistance heating boat. After depressurizingthe vacuum chamber to 4×10⁻⁴ Pa, the foregoing heating boat in whichAlq₃ was charged was heated via electricity application to conductevaporation on the foregoing first electron transport layer at adeposition rate of 0.1 nm/sec to form the second electron transportlayer having a film thickness of 40 nm.

In addition, the substrate temperature during evaporation was roomtemperature. Subsequently, lithium fluoride and aluminum were depositedso as to give thicknesses of 0.5 nm and 110 nm, respectively to form acathode. Thus, organic EL element 5-1 (Comparative example) wasprepared.

Preparation of Organic EL Element 5-2 The Present Invention

Organic EL element 5-2 was prepared similarly to preparation of organicEL element 5-2, except that compound 5-1a as a comparative organic ELelement material was replaced by compound 5-1b as an organicelectroluminescent element material of the present invention.

<<Evaluation of Organic EL Element>>

As to evaluations of the resulting organic EL elements 5-1 and 5-2, theevaluations were made by the same method as used in Example 1. Thevalues of externally taking-out quantum efficiency and light emissionlifetime are represented by the relative values when those of organic ELelement 5-1 each is set to 100.

The obtained results are shown below.

Externally Hole taking-out Light Organic EL transport quantum emissionelement No. material efficiency lifetime Remarks 5-1 5-1a 100 100Comparative example 5-2 5-1b 102 321 Present invention

As is clear from the above-described, it is to be understood thatorganic EL element 5-2 prepared with 5-1b as an organic EL elementmaterial of the present invention exhibits drastically longer lightemission lifetime in comparison to organic EL element 5-1 as acomparative example.

1. An organic electroluminescent element material comprising asynthesized polymer from at least one monomer having an impurity contentof 1000 ppm or less.
 2. The organic electroluminescent element materialof claim 1, wherein the at least one monomer has an impurity content of1000 ppm or less.
 3. The organic electroluminescent element material ofclaim 1, wherein the at least one monomer comprises a reactivesubstituent.
 4. The organic electroluminescent element material of claim1, the polymer comprises a partial structure represented by thefollowing Formula (1):—Ar1-N (Ar3)-Ar2-  Formula (1) wherein each of Ar1 and Ar2 independentlyrepresents an arylene group or a heteroarylene group, and Ar3 representsan aromatic hydrocarbon group or an aromatic heterocyclic group.
 5. Anorganic electroluminescent element comprising the organicelectroluminescent element material of claim
 1. 6. The organicelectroluminescent element of claim 5, comprising a phosphorescenceemission compound.
 7. The organic electroluminescent element of claim 5,prepared with a solution comprising the organic electroluminescentelement material of claim
 1. 8. The organic electroluminescent elementof claim 5, producing white light emission.
 9. A method of manufacturingan organic electroluminescent element, comprising the step of: using areaction solution for a polymer to be synthesized from at least onemonomer having an impurity content of 1000 ppm or less to prepare theorganic electroluminescent element of claim
 5. 10. A display devicecomprising the organic electroluminescent element of claim
 5. 11. Anilluminating device comprising the organic electroluminescent element ofclaim
 5. 12. The organic electroluminescent element of claim 6, preparedwith a solution comprising the organic electroluminescent elementmaterial of claim 1.